The present disclosure relates generally to micro electromechanical (MEM) switches and, more particularly, to a multiposition MEM switch.
Advances in integrated circuit technology in recent years have led to the development of micro electromechanical systems (MEMS), featuring devices of micrometer dimensions which can be actuated and controlled using mechanical, electrostatic, electromagnetic, fluidic and thermal methods. MEMS manufacturing technologies are a combination of the more established semiconductor microfabrication techniques with the newer developments in micromachining.
One example of a MEM device is a cantilevered beam switch having one end anchored to a substrate material, such as silicon. The free end of the beam serves as a deflection electrode which, when a voltage source is applied thereto, deflects as a result of the electrostatic forces on the beam and a field plate, thereby making contact with a stationary electrode. When the voltage source is removed, the beam returns to its xe2x80x9crigidxe2x80x9d state due to the restoring forces therein and the switch contacts are opened.
Although advances in MEM technology have been considerable in recent years, the technology is not without its drawbacks. For example, one of the most insidious problems facing manufacturers of MEMS devices is stiction, which occurs when a surface of a micromachined part (such as a cantilever beam) becomes fused or bonded to an adjacent surface of the structure. Stiction can often result from conditions such as surface roughness, humidity, applied voltage and capillary forces during the manufacturing process. The greater the number of stiction problems occurring in a device, the greater the overall effect on the yield of the device becomes. In addition, the physical geometry of a component itself may also have an effect on its susceptibility to stiction; switches of the cantilevered type may undergo warpage due to repeated mechanical stresses on the beam. As such, it is desirable to provide a switch design which minimizes the susceptibility to stiction.
Other difficulties associated with beam switches may include: material fatigue, space constraints (from the requirement for anchoring points), the creation of parasitic inductances and resonant frequency problems. It is also desirable, therefore, to provide a MEM switch which addresses the aforementioned concerns.
In an exemplary embodiment, a micro electromechanical switch has a guidepost formed upon a substrate. A signal transmission line is formed on the substrate, with the signal transmission line having a gap and forming an open circuit. The switch further includes a switch body having a via opening formed therein, with the switch body being movably disposed along a length defined by the guidepost. The guidepost is partially surrounded by the via opening. In a preferred embodiment, a field plate is formed on the substrate and aligned electrostatically attractably apart from the switch body. An electrostatic attraction between the field plate and the switch body causes the switch body to close the gap in the signal transmission line.